Field of the Invention
The invention relates to a chip card having a contact zone, in a region of which an electrically conductive lacquer is applied.
Chip cards have been known for a long time and are used, for example for the purpose of making payments, in particular in public telephone systems. Chip cards are also used as identification cards.
Chip cards often include an integrated circuit, which can be accessed via an electrically conductive contact zone provided on the surface of the chip card. The contact zone consists of individual contacts which are electrically insulated from one another.
It is known to provide the contacts of the contact zone with an electrically conductive lacquer. It is also possible to color this lacquer. As a result, the contact zone itself can serve as an information carrier if, for example, the logo of the manufacturer of the chip card is printed onto the chip card using the conductive lacquer.
The electrically conductive lacquer is in this case made as a lacquer to which conductive particles are added. It is for instance known to use carbon for black lacquer.
The above described chip cards of this general type have the disadvantage that the lacquer of the contact zone is subject to high frictional wear. Furthermore, it often occurs that the electrically conductive particles oxidize, so that the resistance during access to the contact zone rises in such a way that a satisfactory functioning of the chip card is no longer ensured. In addition, such a surface is dull and matte and thus unattractive.
Published European Patent Application EP 0 340 421 A2 discloses a conductive lacquer which contains a salt based on a tetracyanoquinodimethane complex, a high molecular weight compound and a solvent. The compound contains a surfactant or a silicone oil and/or further substances such as acetals, esters and siloxanes.
Published French Patent Application FR 2 671 417 A1 describes a method of producing a memory card. A dielectric lacquer layer is deposited on an integrated circuit, specifically excluding contact regions. Read/write contacts are then provided with a conductive lacquer, which is in turn covered with a second layer of a dielectric lacquer.
It is accordingly an object of the invention to provide a chip card and a method of its production which overcome the abovementioned disadvantages of the heretofore-known devices and methods of this general type and, which ensure long-term reliability.
With the foregoing and other objects in view there is provided, in accordance with the invention, a chip card, including:
a contact zone having a region;
an electrically conductive lacquer applied to the region, the electrically conductive lacquer based on an intrinsically conductive plastic material; and pigments added to the electrically conductive lacquer.
In accordance with another feature of the invention, there is provided an electrically nonconductive lacquer applied to the region of the contact zone, conductive particles disposed in the electrically nonconductive lacquer, and the electrically conductive lacquer forming a covering for the conductive particles.
With the objects of the invention in view there is also provided, a method of lacquering a contact zone, which includes:
adding pigments to an intrinsically conductive plastic material for forming an electrically conductive lacquer; and
applying the electrically conductive lacquer on a contact zone.
In accordance with another mode of the invention, there is further provided the step of applying an electrically nonconductive lacquer on the contact zone, the electrically nonconductive lacquer including conductive particles having a covering made from the electrically conductive lacquer.
With the objects of the invention in view there is furthermore provided a method of producing a chip card, which includes:
providing a chip card having a contact zone with contacts and interspaces therebetween;
providing a lacquer based on an intrinsically conductive plastic material with pigments added thereto;
covering the interspaces with a stencil; and
coating the contact zone, while the interspaces are covered by the stencil, with the lacquer.
In accordance with another mode of the invention, the step of coating includes coating the contact zone with an electrically nonconductive lacquer having conductive particles with a covering of the lacquer based on the intrinsically conductive plastic material.
In accordance with the invention, an intrinsically conductive plastic material, such as polyaniline, is used for lacquering the contact zone. The term xe2x80x9cintrinsically conductivexe2x80x9d defines that the plastic material itself conducts without additional conductive particles having to be added to it. The lacquers of this type have a good adhesiveness or adherence to customary materials of contact surfaces of the contact zone.
Further, in accordance with the invention, nonconductive pigments can be added to the lacquer. With such a pigmentation, virtually any color can be achieved. Even luminous colors can be produced when suitable pigments are used. Such colors are impossible to realize on chip cards known in the prior art. In particular green color shades can be produced especially simply, because of the inherent green color of the polyaniline (PANI) that can be used in accordance with the invention.
In addition, through the use of a suitable selection of the lacquer component, the quality of the surface of the chip cards according to the invention can be set to be sufficiently hard. As a result, frictional wear will occur only to a small extent.
According to the invention, an electrically nonconductive lacquer with electrically conductive particles may also be used, wherein the particles are covered with intrinsically conductive plastic material. Silver particles may for example be used as the electrically conductive particles. Given complete wetting or covering of the conductive particles by the intrinsically conductive plastic material, an abrasion-resistant lacquered contact zone, which has a high reliability, is thus produced.
Furthermore, the invention also teaches the use of an intrinsically conductive plastic material for lacquering a contact zone, in particular the contact zone of a chip card or smart card. According to the invention, an intrinsically conductive plastic material, to which in particular nonconductive pigments are added, can also be used for lacquering other contact surfaces.
Finally, the invention also comprises a method of producing a chip card, which has the following steps:
providing a chip card,
lacquering the contact zone of a chip card, interspaces between individual contacts of the contact zone being covered by a stencil, wherein the lacquering is carried out using a lacquer based on an intrinsically conductive plastic material.
As a result, in the case of the process according to the invention, the conductivity of the contacts is maintained and a short circuit between the individual contacts is avoided. Using the process according to the invention, durable chip cards that are also protected against frictional wear can be produced.
Thus, using the invention, the contact surfaces of a chip card module can be used as an advertising surface. A decoration of the contact surface can be achieved while at the same time ensuring the functionality of the contact surface. It is thus possible to produce colored symbols, emblems and the like in a durable and impressive manner, especially on golden or silver contact surfaces of a chip card. The variety of colors is in this case not restricted, as is the case with the chip cards known in the prior art, and it is in particular possible to produce luminous or bright colors.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a chip card and a corresponding method for producing a chip card, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.